The use of light diffusers is common in backlight illumination, which is frequently found in liquid crystal displays (LCDs). For visible light, the criterion of diffuser design is significantly different than that for ultraviolet (UV) radiation. This is largely related to the fact that UV transparent materials are harder to manufacture than corresponding materials for visible light. Further, the transparency of UV materials is typically inferior to the transparency of materials to visible light. In addition, the UV transparent materials are expensive compared to materials transparent to visible light.
Recently, various improvements to backlight visible light illumination design have been proposed. For example, collimating multi-layer optical film (CMOF) provides a cost efficient light management for LCD backlights with integrated optical films. These films provide diffusive capability to LCD backlight illuminators. CMOF is based on multi-layer optical film technology that is used to make current display films, such as dual brightness enhancement film (DBEF), reflective polarizers, and enhanced specular reflector (ESR) films. The CMOFs are used in a new backlight architecture developed by 3M™ and branded as Air Guide. CMOF technology combines two types of nanotechnologies: nanolayer optics and ultra-low refractive index nanofoam. The CMOF film is attached directly to the LCD panel, replacing several separate films used in current light emitting diode (LED) backlight designs. The new design uses a hollow cavity with no free-floating films and no solid light guide. In the Air Guide design, light is spread through the air of the cavity between the LCD panel and the highly reflective film. FIGS. 1A and 1B illustrate the schematics of a previous LED backlight design and 3M's Air Guide design, respectively.
Another traditional design for diffusive wave guiding is shown in FIGS. 2A and 2B. In this design, the LED lights are positioned at a side of the diffuser (see FIG. 2B, for example). The diffuser is composed of several layers: a sheet with micro-features, reflecting and light guiding sheets, and a diffusive sheet followed by optional prismatic and other diffusive sheets. For success of such a design, good light reflective and light transparent materials have to be employed, which is difficult to achieve for ultraviolet illumination.
Currently, UV devices capable of operating to sterilize mobile phones are available, such as the UV Sterilizer for iPhone from Sinco-Elec. Co. This UV sterilizer is a desktop unit that allows a user to place a mobile phone into the sterilizer for about five minutes for UV sterilization. The device turns a blue LED on to indicate the sterilization is in process. Completion of the sterilization process is indicated by the blue indicator LED turning off. The device does not utilize low voltage light emitting diodes and cannot be used as a carry-case.